Spring Dead Spot of Buffalograss Caused by Ophiosphaerella herpotricha in Kansas and Oklahoma

Buffalograss (Buchloe dactyloides) is widely planted in the Great Plains region of the United States as an amenity turfgrass. In May 1993, we observed circular dead spots in buffalograss lawns that were resuming growth following winter dormancy. The dead spots, 12 to 40 cm in diameter, were slowly filled in by buffalograss during the summer but reappeared in the same locations the following spring. Roots and stolons at the patch margins were colonized by darkly pigmented, ectotrophic fungal hyphae. Ophiosphaerella herpotricha, a cause of spring dead spot disease of bermudagrass (Cynodon spp.), was consistently isolated from diseased buffalograss roots collected in Kansas and Oklahoma. Identification of O. herpotricha was confirmed by the use of species-specific polymerase chain reaction (PCR) primers. To complete Koch's postulates, a 3-year-old stand of buffalograss cv. Sharp's Improved located in Manhattan, KS, was inoculated in September 1994 with O. herpotricha. Eleven soil cores, 10 cm in diameter × 8 cm deep, were removed at 1.2-m intervals across the turf. Five grams of oat seed infested with O. herpotricha (isolate KS221) wasadded to each hole and the soil plug was reinserted. For controls, 5 g of sterile oat seed was inserted in the bottom of each of 11 additional holes. No symptoms developed the following spring, but circular dead spots, ranging in size from 18 to 43 cm in diameter, were observed at 10 of 11 and 6 of 11 inoculation sites in May 1996 and 1997, respectively. No spots were noted in areas amended with sterile oats. O. herpotricha was consistently isolated from the roots at the margins of the patches. This is the first report of O. herpotricha causing spring dead spot in buffalograss.